Electric communication cable



April 19, 1932.

ELECTRIC COMMUNICATION CABLE Filed Aug. 2l, 1929 um ll'llllllllllllllllll /Nl/f/V To@ E. KAEMPF ATTORNEY Patented Apr. 19, 1932 l UNITED .STATES PATENT OFFICE man. umn, or AImwYcn, LONDON, ENGLAND, AssreNon. Irio wEsrEzaN ELECTRIC conan, mooaronarnn, or NEW Yonx, N. Y., A coEEonATIoN or NEW Yom:

ELECTRIC COMMUNICATION CABLE Application lell4 August 21, 1989, Serial No. 887,344, and in Great Britain November 13, 1928.

This invention relates to electric. communication cables in which the conductors are grouped in pairs or multiples of pairs.'

In order to obtain eiclent or distortionless transmission over-a cable of. this type it is necessary that the capacities within the cable be uniformly distributed. To this end l it is usual to expend great care in obtaining uniformity of the conductors themselves and in "the insulating materials, usually paper, which surround them. However, in order to vreduce cross talker capacity unbalance in 'the cable, it isnecessary to use different various groups. `The-separator is selected for thispurpose in respect to its dielectric properties and in respect to the capacity between the conductors of groups so that the difference in capacity due to the difference in twist lmay be compensated for by the difference in the dielectric properties of the separators. A compensating effect may be obtained by the insertion of strips of varying thickness and/or volume and/or composition and/or specific weight and/or form, between the two wires 'of` a pair of conductors or by inserting such material between the two conductors of pairs having certain twists and omitting such material between the two conductors of pairs having other twist'lengths.

The present invention relates particularly to'cables in which the conductors are arranged in what is usually termed stars. that is, groups of four elements, each consisting either of a single wire, or units of wires, the four elements being so arranged as to occupy the four corners of a square and beonsequently the great care ing twisted together about their common center. In the most simple type of star, cons1st1ng of four conductors, there are three possible circuits, two pair circuits and one superimposed circuit commonly called phan tom circuit. The two conductors diagonally opposite each other form a pair. Each individual star of whatever composition is characterized by the length of its twists.

It is known that in such star units the geometrical -regularity and the mechanical stathread maybe used in some stars and not inY others or dissimilar strings aud/or threads may be used in stars of diierent twist lengths lin order to obtain equality of capacities between the conductors `in various stars.

Thus by selecting or varying the diameter, and/or volume and/or specific weight and/o1` composition and/or form of the central .strings used in the star quads the compensation may beeifected. Still another way of carrying out the invention is to use different numbers of strings situated in the different quads;also the complete compensation may be effected byusing some or al1 of the above methods .i'n combination.

The invention will now be described in connectionwith specific and preferred embodiments and reference will `be made for this purpose to the attached drawings in which y Fig. 1 is a simplified showing of a portion of a telephone cable to which the present invention may be applied and in which the conductors are twisted together in pairs;

Fig. 2 isa sectional view of a twisted pair separated in accordance with the invention;

Fig. 3 is a simplified showing of a telephone cable in which the conductors are grouped in stars; and

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Fig. 4 is a sectional view of a star unit Vof conductors.

Referring toFig. 1, the cable 10 comprises a plurality of twisted pairs of conductors 11, two of which, 12 and 13, are shown as having different length of twist in order to prevent cross talk between the pairs. The pair 14 has been illustrated more in detail in order to more clearly show the feature of the invention. This pair comprises conductors 15 and 16, each of which has a central conducting wire surrounded by paper insulation. This paper insulation may be in the form of paper strips such as shown :1t-17 and 18 wound about the conducting wires, preferably with an annular air space between the wire and the main body of the paper insula- 'tion as more clearly shown in Fig. 2. Be'- tween the insulated conductors 15 and 16 is placed a separator 19 by means of which the desired compensation is obtained in accordance with the invention. This separator may be of any suitable insulating material such as, for example, paper andmay be in the form of a single strip or may be creased into several layers or it may comprise a number of strips placed together to provide the desired separation. Thus in a pair with a certain twist, a smgle layer may be desirable, whereas in another pair with a different twist the separator 19 may comprise a number of layers to compensate for the difference in capacity between the conductors o the two pairs'due to their difference in twist. The compensation may be obtained by varying the separator 19 in other ways as for example, byvarying the thickness or the width of the tape 19 or by varying the density of the material of the separator or by using materials having different dielectric constants. Any two or more of these methods may be combined for the attainment of the desired compensation.

In Fig. 3 is shown a portion of a cable 50 having the conductors arranged in star quads4 51. Two such quads 52 and 53 are shown as having different lengths of twist and a quad 54 is shown more in detail as comprising paper insulated conductors 55, 56, 57 and58 similar to the conductors shown in Fig. 1. A section of thisv quad is shown in Fig. 4 which also shows a separator 59 placed in the geometric center of the star. This separator 59 besides serving the purpose of giving mechanical stability to the quad also afects the capacity between the conductors of the pairs of the quad, that is, between conductors and 57, forming one pair and 56 and 58 forming the other pair. Also in this case, the separator 59 may be varied in the quads in ence in length of twist and the consequent difference in capacity between the conductor pairs. Thus the form or the volume of the separator may be varied; different materlals order to compensate for the differ-- may be used such as cotton or silk; the cord may be impregnated with different substances to vary its dielectric constant or may be more or less compressed; and any two or more of these methods may be combined for the purpose of the invention.

What is claimed is:

l. In a communication cable, insulated conductors twisted into groups with different lengths of twist, continuous elements of insulating material,said elements having different dielectric properties, one of said elements being placed within each of said groups so that the dierences in said properties are effective in substantially compensating for the difference in capacities between the conductors in said groups which is due to the difference in length of twist of said groups.

2. A communication cable having insulated conductors-twisted into groups, the length of twist of one group being different from that ,of another group and each of said groupshincluding a continuous element of insulating-material placed between a pair of its insulated conductors, one of said elements in one of said groups forming a dielectric between its pair of conductors, and another of said elements in another of said groups forming a dielectric different from that of the first said element, to reduce the dierence in capacities between said pairs of conductors in said two groups, which would otherwise have existed Adue to the dierence in length of twist of said groups.

3. A communication cable comprising a plurality of insulated conductors, twisted into star quads having twists of dierent lengths and having a cord placed centrally within each of said quads the cord of one of said quads having an electrostatic capacity effect different from that of the cord of another of said quads to substantially compensate for the dierence in capacitiesof said quads due to the difference in their length of twist.

4. A communication cable in accordance with claim 2 in which said continuous elements have dierent dielectricconstants.

5. A communication cable in accordance with claim 2 in which said continuous elements are composed of different materials and are of different volumes.

6. A communication cable in accordance with claim 3 in which said cords are composed of dilerent materials.

7. A communication cable in accordance with claim 3 in which said cords are composed of different materials and have different dimensions.

In witness whereof I hereunto subscribe my name this thirty-first day of July, 1929.

EMIL KAEMPF.

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